[First classification criteria for diseases caused by calcium pyrophosphate deposition (CPPD)-Translation, explanation and assessment]. / Erste Klassifikationskriterien für durch Kalziumpyrophosphatablagerungen verursachte Erkrankungen ­ Übersetzung, Erläuterung und Bewertung.

AIM: For diseases caused by calcium pyrophosphate deposition (CPPD), validated classification criteria were previously lacking. In this article the recently developed and validated classification criteria are translated, explained, and assessed. METHODS: In recent years a multinational research group developed classification criteria for CPPD disease with the support by the European Alliance of Associations for Rheumatology (EULAR) and the American College of Rheumatology (ACR), following an established method. The developed criteria were finally validated in an independent cohort. The translation and annotation of the new first classification criteria were carried out in an iterative procedure in consensus with the authors. RESULTS: The presence of a crowned dens syndrome or calcium pyrophosphate crystals in the synovial fluid in patients with pain, swelling or sensitivity of the joints (entry criterion) is sufficient for the classification as CPPD disease, where the symptoms cannot be completely explained by another rheumatic disease (exclusion criterion). If these symptoms are not present, a count of more than 56 points based on weighted criteria comprised of clinical features and the results of laboratory and imaging investigations can be included for classification as a CPPD disease. These criteria had a sensitivity of 92.2% and a specificity of 87.9% in the derivation cohorts (190 CPPD cases and 148 mimics), whereas the sensitivity was 99.2% and the specificity 92.5% in the validation cohorts (251 CPPD cases and 162 mimics). CONCLUSION: The ACR/EULAR classification criteria 2023 of a CPPD disease will facilitate clinical research in this field. The use in the clinical routine will show how practical the criteria are.

High prevalence of chondrocalcinosis and frequent comorbidity with calcium pyrophosphate deposition disease in patients with seronegative rheumatoid arthritis.

BACKGROUND: The crystal-induced calcium pyrophosphate deposition disease (CPPD) clinically appearing as pseudogout differs from the mere radiographic finding of chondrocalcinosis (CC) but may cause symptoms resembling rheumatoid arthritis (RA). OBJECTIVE: To study the prevalence of CPPD and CC in rheumatic diseases focusing on differences between seropositive and seronegative RA. PATIENTS AND METHODS: In a retrospective study design, we analysed records and radiographs of consecutive new patients presenting to our centre between January 2017 and May 2020. 503 patients were identified based on expert diagnoses: 181 with CPPD, 262 with RA, 142 seropositive (54.2%) and 120 seronegative RA, gout (n=30) and polymyalgia rheumatica (n=30), mean symptom duration <1 year in almost all patients. RESULTS: The majority of patients had only one rheumatological diagnosis (86.9%). Most patients with CPPD (92.6%) had radiographic CC, primarily in the wrists. The prevalence of CC was higher in seronegative (32.3%) than in seropositive RA (16.6%), respectively (p<0.001). Patients with CPPD were older (p<0.001) and had acute attacks more frequently than patients with RA (p<0.001), who had symmetric arthritis more often (p=0.007). The distribution pattern of osteoarthritic changes in radiographs of hands and wrists differs between patients with RA and CPPD. CC was present in more than one joint in 73.3% of patients with CPPD, 9.6% with seropositive and 18.7% with seronegative RA. DISCUSSION: CPPD and CC were more frequent in seronegative versus seropositive RA. Symmetry of arthritis and acuteness of attacks differentiated best between CPPD and RA but localisation of joint involvement did not. Co-occurrence of both diseases was frequently observed.